Field of the Invention
The invention relates to an electric power steering device applying, from a motor, a force (steering assist force) that assists a driver's steering during operation of a steering handle.
Description of the Related Art
An electric power steering device provided in a vehicle generates a steering assist force by driving an electric motor. As the electric motor, for example, a three-phase alternating current (AC) motor having U-phase, V-phase and W-phase windings is used. The three-phase AC motor cannot be driven any more in normal control when an abnormality such as disconnection or the like occurs in any phase. Patent Documents 1 and 2 disclose a control (referred to as abnormality occurrence state energization control) driving a motor (brushless motor) using the remaining two phases other than a phase (referred to as abnormal phase) in which an abnormality has occurred. In the inventions of Patent Documents 1 and 2, in cases where the motor is driven by the abnormality occurrence state energization control, when a magnetic pole of a rotor passes over, for example, a U-phase winding, V-phase and W-phase currents are increased.